This invention is directed to devices and equipment for collecting bulk solids, for example, process dust coming from a dust generating tool, such as a sanding machine, where the dust is entrained in a flow of air from the source machine, and is separated out at the dust collection equipment where the dust precipitates into a drum, barrel, or similar container. The invention is more specifically directed to a compact and efficient device to be used between a tool and a vacuum source, e.g., shop vacuum, to separate and collect the dust from the airstream emerging from the tool before the air stream reaches the vacuum source. The invention is likewise concerned with a simple and straightforward dust separation assembly that can be associated with a tool that has a duct from with the air stream plus entrained dust particles proceed.
The invention is also concerned with a simple and straightforward silencer device that can be dropped in to the cylindrical filter of a cyclonic dust collection system to reduce the equipment noise by 3 to 8 dB.
For many types of machines for processing a workpiece, some means has to be provided to dispense with the grindings, chips, and particulate matter that is generated by the machine during operation. For example, in the case of wood working machines, such as sanders, joiners, and the like, wood that is removed from a workpiece has to be collected and removed from the work area so as to avoid either a breathing hazard for the workman or a fire hazard. More specifically, in the case of portable equipment, sanders and buffers, it is conventional to draw off the dust that is generated by the machines and then send the air that is carrying the dust into a filter bag arrangement, or to draw off the dust through a flexible hose or conduit. In such case, the conduit or hose extends from a dust outlet duct of the machine to a collection station. In the case of smaller equipment, e.g., palm sanders or trim sanders, the stream of air is pumped through a flexible hose conduit, with the entrained process dust, to a piece of equipment that provides suction and some filtering, e.g., a shop vacuum. This arrangement requires that the shop vacuum be cleaned and emptied regularly, to keep the wood dust from clogging the machine.
It has sometimes been desirable to collect bulk solids (e.g., dust) directly inside a drum or barrel, or in a plastic bag or liner in the drum.
An example of a cyclonic dust collection system is shown in U.S. Pat. No. 6,833,016, which is incorporated herein by reference. In the dust collection station described therein, the air flow and entrained process dust are drawn through a cyclone separator disposed atop a storage drum or barrel. The process dust falls into a durable plastic film bag or liner in the barrel, and the air then proceeds to a pumping and filtering arrangement, where the dust-free air is discharged back into the ambient environment. Means can be included to maintain a vacuum or negative pressure as a bag hold-down feature, to draw and hold the bag against the inside of the barrel. Then, when the bag has been filled to its capacity, the bag can be tied off and lifted out, which eliminates the need to dump the barrel. This also avoids exposure to the operators of the process dust when the collected dust is removed from the barrel for disposal.
In practice, no one has attempted to use a true cyclonic separator as an intermediate dust separation and collection device between the dust producing tool and the shop vacuum or other source of suction that accepts the dust and air stream from the tool. One proposed auxiliary dust collection receptacle, to be situated between a dust producing tool and a shop vacuum cleaner, is described in U.S. Pat. No. 6,027,541 to Siemers. In that proposed arrangement, a special lid is provided for a conventional plastic trash can. The lid has inlet and outlet sockets for hoses, one coming from the dust producing tool and the other going to the shop vacuum. The air flow is intended to produce a cyclonic air movement, with the dust precipitating from the air flow in the trash can. This arrangement is only mildly effective, as only about 50 percent of the airborne dust is separated out, with the remaining 50 percent continuing to the shop vacuum. Also, because the trash can itself is both the vortex chamber and the dust collection chamber, there is a low limit to the amount of dust that can be collected; at or above a partial fill level, the air stream picks up as much dust in the trash can as it drops.
This arrangement also does nothing to reduce the level of process noise from operation of the dust collection equipment.